<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="./styles/index.css" />
    <title>Document</title>
</head>

<body>
    <div id="app" class="score-case">
        <div class="table">
            <table>
                <thead>
                    <tr>
                        <th>编号</th>
                        <th>科目</th>
                        <th>成绩</th>
                        <th>操作</th>
                    </tr>
                </thead>
                <tbody v-if="list.length > 0">
                    <tr v-for="(item, index) in list" :key="item.id">
                        <td>{{ index }}</td>
                        <td>{{ item.subject }}</td>
                        <td :class="{red: item.score < 60}"> {{ item.score }} </td>
                        <td><a href="#" @click="del(item.id)">删除</a></td>
                    </tr>
                </tbody>
                <tbody v-if="list.length === 0">
                    <tr>
                        <td colspan="5">
                            <span class="none">暂无数据</span>
                        </td>
                    </tr>
                </tbody>

                <tfoot>
                    <tr>
                        <td colspan="5">
                            <span>总分：{{ total }}</span>
                            <span style="margin-left: 50px">平均分：{{ average }} </span>
                        </td>
                    </tr>
                </tfoot>
            </table>
        </div>
        <div class="form">
            <div class="form-item">
                <div class="label">科目：</div>
                <div class="input">
                    <input type="text" placeholder="请输入科目" v-model.trim="subject" />
                </div>
            </div>
            <div class="form-item">
                <div class="label">分数：</div>
                <div class="input">
                    <input type="text" placeholder="请输入分数" v-model.number="score" />
                </div>
            </div>
            <div class="form-item">
                <div class="label"></div>
                <div class="input">
                    <button class="submit" @click="add">添加</button>
                </div>
            </div>
        </div>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>

    <script>
        const app = new Vue({
            el: '#app',
            data: {
                list: [
                    { id: 1, subject: '语文', score: 20 },
                    { id: 7, subject: '数学', score: 99 },
                    { id: 12, subject: '英语', score: 70 },
                ],
                subject: '',
                score: ''
            },
            methods: {
                del(idx) {
                    this.list = this.list.filter(item => item.id !== idx)
                },
                add() {
                    if (this.subject === '' || this.score === '') {
                        alert('请填写完整信息')
                        return;
                    }
                    this.list.push({
                        id: +new Date(),
                        subject: this.subject,
                        score: this.score
                    })
                    this.subject = ''
                    this.score = ''
                }
            },
            computed: {
                total() {
                    return this.list.reduce((sum, item) => sum + item.score, 0);
                },
                average() {
                    if (this.list.length === 0) return 0;
                    // toFixed(2) 保留两位小数
                    return (this.total / this.list.length).toFixed(2);
                }
            }
        })
    </script>
</body>

</html>